chore(deps): update dependency pandas-stubs to v3.1.0.261029 (#302)

chore(deps): update dependency pandas-stubs to v3.1.0.261029 (#302)

* chore(deps): update dependency pandas-stubs to v3.1.0.261029

* chore(types): refresh pandas-stubs snapshots

pandas-stubs 3.1 widens the inferred scalar union in Series.iat.
Keep the exact baseline aligned without changing runtime code.

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Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: Jérôme Benoit <jerome.benoit@piment-noir.org>